1. Field of the Invention
The present invention relates to devices used for forming uniform powder layers on objects, and more particularly, to a charged powder supply device.
2. Description of Related Art
Along with the rapid development of electronic industries, electronic products are becoming lighter, thinner, shorter and smaller and developed towards high performance, high function and high speed.
In a conventional LED fabrication process, phosphor is formed on an object by dispensing or coating. During coating, it is difficult to control the coating amount of phosphor in different areas of the object and consequently the phosphor in different areas often has different thicknesses. Also, the phosphor may be distributed on LEDs by a diffusion process. However, it is difficult to control the diffusion direction of the phosphor. As a result, the LEDs have different amount of phosphor formed thereon.
FIG. 1 shows a conventional coating process in other industries. Referring to FIG. 1, a powder supply device 1 has: a fluidized board 10 having a plurality of micro-holes (not shown), a supply portion 11 disposed below the fluidized board 10, and a receiving member 12 disposed over the fluidized board 10 and having a plurality of objects 13 to be coated. The fluidized board 10 is used for carrying powder 8.
In operation, air is supplied from one side of the fluidized board 10 by the supply portion 11 so as to provide an air flow A to a lower side of the fluidized board 10. The air flow A then passes through the micro-holes of the fluidized board 10 to cause the powder 8 to rise up and be attached to the receiving member 12.
However, since it is difficult to control the direction of the air flow A after it passes through the micro-holes of the fluidized board 10, undirected flows, such as turbulent flows, can easily occur, especially after the air flow A arrives at and then bounces back from the receiving member 12. Consequently, the powder 8 cannot rise up and be distributed uniformly on the receiving member 12. Accordingly, the powder 8 cannot be uniformly attached to the objects 13.
Further, since the micro-holes of the fluidized board 10 have a very small size, some of them may be blocked by the powder 8 in operation and prevent the air flow A from passing through, thereby preventing the powder 8 from being uniformly attached to the receiving member 12.
If the coating process shown in FIG. 1 is applied to the manufacturing process of LEDs, since the air flow A, after passing through the fluidized board 10, cannot flow unidirectionally, the powder 8 will not rise uniformly. As a result, the powder 8 will not be distributed uniformly on the LEDs disposed on the receiving member 12, and the LEDs do not have highly uniform phosphor formed thereon.
Therefore, how to overcome the above-described drawbacks has become urgent.